JP2001357506A - Rotary head drum device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress stress deformation due to force-fitting of a shaft and decrease in a shaft binding force or deformation of a formed product which are due to thermal expansion or contraction due to change in temperature used after the force-fitting, in the case of forming a fixed drum with a resin. SOLUTION: A tapered part 6a is coaxially provided between the shaft force- fitting part 6c and the sliding contact part 6b for a tape, in the fixed drum 6, for the purpose of dispersing and absorbing a deforming stress.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary head drum device for recording and reproducing information with a magnetic head using a tape-shaped recording medium, for example, a rotary head drum device such as a video tape recorder.

[0002]

2. Description of the Related Art A rotary head drum device for recording and reproducing information on a tape-shaped recording medium by rotating a magnetic head has been widely used, for example, because it can perform high-speed recording of information. High-density recording
Reproduction is required, and a highly accurate rotary head drum device is required.

FIG. 6 is a perspective view showing a conventional rotary head drum device. FIG. 7 is a sectional view showing the shape of the fixed drum 2 in FIG. FIG. 8 is a perspective view showing the shape of the fixed drum. As shown in FIGS. 6 to 8, the rotary head drum device includes a rotary drum 1, a fixed drum 2, and a shaft 5.

The shaft 5 has a shaft press-fitting portion 2 at the center of the fixed drum 2.
c, and rotatably supports the rotating drum.
A magnetic head 3 is mounted on the outer peripheral surface of the rotary drum 1 and performs high-speed rotation to record and reproduce information relative to a tape-shaped recording medium 4 at a high speed. The tape-shaped recording medium 4 slides in contact with a part of the outer peripheral surface of the fixed drum 2 and runs. In order to realize the stable running, the fixed drum 2 is provided with a tape guide 2b at a tape sliding contact portion thereof. I have. As shown in FIG. 8, the fixed drum 2 includes
A cutout portion 2a is formed in a part of the outer peripheral surface for passing wiring for transmitting and receiving information to and from the magnetic head 3.

Although the rotary head drum device generally requires high dimensional accuracy, the fixed drum 2 particularly requires high dimensional accuracy in the tape sliding portion including the tape guide 2b. In order to achieve this dimensional accuracy, distortion that occurs when the rotary head drum device is fixed also poses a problem. For this reason, there is known a rotary head drum device in which a slit shape is provided in the vicinity of a fixed portion of a fixed drum, and the rigidity is reduced to absorb the distortion at the portion (JP-A-4-30361).

The conventional rotary head drum device is manufactured by cutting an aluminum alloy. However, high precision processing of a complicated shape is required, and the manufacturing cost is increased due to single-piece processing. There was a problem. In order to solve this problem, a resin rotary head drum device that can be manufactured only by molding processing has been proposed (Japanese Patent Application Laid-Open No. 55-160353). By forming the rotary head drum device from the resin as described above, cost reduction and weight reduction can be achieved. Further, it is also possible to integrally form the rotary head drum device and the drum base or the like, and there is an advantage that the cost including the peripheral portion of the rotary head drum device can be reduced.

[0007]

However, when the fixed drum 2 is formed of resin, in addition to the distortion generated when the rotary head drum device is fixed, the distortion of the fixed drum 2 due to the press-fitting of the shaft 5 and the fastening of the shaft are performed. The problem is the decrease in power.

First, resin generally has a lower mechanical strength than aluminum alloy or the like. Therefore, in order to firmly fix the shaft, the interference at the time of press-fitting the shaft needs to be larger than that of aluminum alloy. is there. For this reason, the distortion amount of the resin molded product is larger than that of the case of the aluminum alloy. As a matter of course, if the interference is reduced, the stress distortion is reduced, but the shaft is not firmly fixed and the shaft fastening force is low.

Next, a resin generally has a large coefficient of linear expansion and an extremely large coefficient of linear expansion than the material of the shaft. There is a problem of distortion generation.

To solve these problems, as a method of increasing the mechanical strength of a resin, it is common practice to use a resin composite material filled with a reinforcing material such as glass fiber or carbon fiber. However, the fixed drum 2 has good sliding properties with the tape-shaped recording medium 4, does not become charged when sliding with the tape-shaped recording medium 4, and can be precision molded. Various characteristics are required. Reinforcing materials that improve mechanical strength with respect to these required characteristics are not always effective. Considering the anisotropy of the reinforcing material, it may be disadvantageous especially in precision molding.

The resin material used for the rotary head drum device is disclosed in JP-A-62-52755, in which the absolute value of the linear expansion coefficient is 10 × 10 ⁻⁶ / K or less.
Japanese Patent Application Laid-Open No. 60-55551 discloses that the coefficient of linear expansion is about 20 × 10 ⁻⁶ / K.
It is disclosed that it is from × 10 ⁻⁶ / K to 25 × 10 ⁻⁶ / K. However, in the above disclosure, there is no description in consideration of fixing the shaft and the resin molded product, and in fact, the linear expansion coefficient of a normally used stainless steel shaft is 16%.
Since it is × 10 ^-6 / K, the problems of reduction in the shaft fastening force and distortion of the resin molded product caused by a difference in the amount of thermal expansion or thermal contraction between the shaft and the resin molded product due to a change in operating temperature cannot be solved. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and can maintain required accuracy even when a large amount of distortion is generated by press-fitting a shaft. It is an object of the present invention to provide a rotary head drum device that can suppress a distortion generated in a tape sliding portion by suppressing a decrease.

[0013]

In order to achieve the above object, a rotary head drum device according to the present invention comprises a rotary drum for supporting a magnetic head, a shaft for rotatably supporting the rotary drum, and a shaft. A fixed drum made of a resin composite material having a shaft press-fitting portion to be fixed and a tape sliding contact portion for guiding the running of the magnetic tape, wherein a linear expansion coefficient in the radial direction near the shaft press-fitting portion is provided. Is substantially equal to the linear expansion coefficient of the shaft.

Further, the rotary head drum device of the present invention
The coefficient of linear expansion in the radial direction near the shaft press-fitting portion is 12 × 10
^-6 / K to 20 × 10 ^-6 / K.

Further, in the rotary head drum device of the present invention, a distortion suppressing portion for suppressing distortion caused by press-fitting of the shaft is provided coaxially between the shaft press-fitting portion of the fixed drum and the tape sliding contact portion. is there.

As described above, by making the linear expansion coefficient of the shaft substantially equal to the linear expansion coefficient of the shaft press-fitted portion, the distortion of the resin molded product or the shaft caused by the thermal strain caused by the change in the operating temperature after the shaft press-fitting. The problem of a decrease in fastening force can be reduced.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 (a) to 3 (b) show the structure of a fixed drum of a rotary head drum device according to the present invention. The fixed drums of the rotary head drum device shown in FIGS. 1A to 3B are all provided with a distortion suppressing unit.
Hereinafter, the first embodiment will be described with reference to these drawings, but the description of the same parts as the fixed drum 2 of the conventional rotary head drum device shown in FIGS. 6 to 8 will be omitted.

First, the fixed drum 6 shown in FIG. 1A will be described. The fixed drum 6 is formed with a shaft press-fitting portion 6c for fixing the shaft 5 at the center, and a tape sliding contact portion 6b formed on the outer peripheral surface for guiding the running of the magnetic tape. A tapered portion 6a is provided coaxially with the shaft 5 between the shaft press-fitting portion 6c and the tape sliding portion 6b.

In the fixed drum, stress distortion caused by press-fitting of the shaft 5 and a change in operating temperature after press-fitting is caused by the shaft press-fitting portion 6c.
To the tape sliding contact portion 6b, but in the above configuration,
Since the tapered portion 6a is provided in the middle of the propagation path of the stress strain, the stress strain is not linearly connected to the tape sliding contact portion 6b, but is dispersed in the axial direction. Further, when the tapered portion 6a is provided, the thickness in the vicinity of the tapered portion 6a is reduced, and the elastic modulus in the radial direction is reduced, so that the distortion can be absorbed. Due to these effects, the tape sliding contact portion 6b
It is possible to reduce the amount of distortion at.

Next, the fixed drum 7 shown in FIG. 2A will be described. In this fixed drum 7, the shaft press-fitting portion 7c
Between the tape-sliding portion 7b, that is, the slit-shaped portion 7 in the propagation path of the stress strain generated from the contact surface with the shaft 5.
a is provided coaxially with the shaft 5. In this configuration as well, like the tapered portion 6a shown in FIG. 1, the slit-shaped portion 7a does not directly connect the strain to the tape sliding contact portion 7b, but can disperse the strain in the axial direction. Further, since the elasticity in the radial direction is reduced by the slit-shaped portion 7a,
Distortion can be absorbed.

Next, the fixed drum 8 shown in FIG. 3A will be described. In the fixed drum 8, the shaft press-fitting portion 8c
And the tape sliding contact portion 8b, that is, in the middle of the propagation path of the stress strain generated from the contact surface with the shaft 5, the step-shaped portion 8a
Are provided coaxially with the shaft 5. By providing the step-shaped portion 8a coaxially with the shaft 5 in this manner, the distortion is not linearly connected to the tape sliding contact portion 8b, and the distortion can be dispersed in the axial direction. In addition, since the transmission path of the distortion between the shaft press-fitting portion 8c and the tape sliding portion 8b becomes longer, the distortion at the tape sliding portion 8b decreases.

In the above example, the taper-shaped portion 6a, the slit-shaped portion 7a, and the step-shaped portion 8a suppress distortion caused by axial press-fitting or a change in operating temperature after press-fitting. Not only that, the shaft press-fitting portion and the tape sliding portion are connected linearly, a thin resin portion is provided between them, or the strain propagation path between them is lengthened. If a shape or a shape combining them is provided, the same effect as described above can be obtained.

FIG. 1B, FIG. 2B, FIG.
As shown in (b), the fixed drums 6, 7, and 8 are formed with cutouts 6d, 7d, and 8d for passing wiring for transmitting and receiving information from the magnetic head. The cutouts 6d, 7d, and 8d are provided so that the elastic modulus of the peripheral portion is reduced when the thickness is partially reduced so that the elastic modulus of the portion is reduced. Therefore, the fixed drums 6, 7,
In the outer peripheral surface of 8, distortion concentrates on the peripheral portions of the notches 6d, 7d, 8d.

However, in the present embodiment, when the tapered shape 6a, the slit shape 7a, and the stepped shape 8a are provided coaxially, the cutouts 6d, 7d, 8d are adjusted so that the elastic modulus is substantially the same. can do. Specifically, the elastic modulus of the tapered portion 6a, the slit-shaped portion 7a, and the step-shaped portion 8a at the peripheral portion of the notch in the circumferential direction is set to be larger than those of the other portions.
It is possible to prevent concentration of distortion at the notches 6d, 7d, 8d. The adjustment of the elastic modulus can be performed by, for example, reducing the taper, narrowing the slit width, or increasing the thickness when providing a step.

Next, an embodiment in which the occurrence of stress distortion is suppressed by adjusting the linear expansion coefficient of the resin composite material for forming the fixed drum will be described.

Normally, in the fixed drum of the rotary head drum device, the expansion or contraction in the radial direction is caused by the fact that the expansion or contraction in the radial direction is caused by the loosening of the shaft or the propagation of distortion to the tape sliding portion requiring high dimensional accuracy. Is more problematic than the expansion or contraction of Therefore, in the present embodiment, the linear expansion coefficient in the radial direction near the shaft press-fitting portion is adjusted to be substantially the same as the linear expansion coefficient of the shaft material to be press-fitted.

In the following, the allowable linear expansion coefficient range of a resin molded product due to a change in the use temperature is estimated. Here, the maximum temperature change to be used is from −40 ° C. to + 80 ° C. In addition, it is difficult to determine the maximum allowable difference in the amount of expansion or contraction between the shaft and the resin molded product due to thermal expansion or contraction due to the problem of mechanical strength of the material and stress relaxation after press-fitting the shaft. It is assumed that it is not more than 1/2 of the maximum allowable amount set in the case of the aluminum alloy fixed drum, specifically, about ± 1 μm.

When the shaft diameter is 4 mm, (δL / L)
× (1 / δT), the coefficient of linear expansion is calculated, and δL = ± 1μ
From m, L = 4 × 10 ³ μm and δT = ± 60 ° C., a linear expansion coefficient of ± 4 × 10 ⁻⁶ / K is obtained. The linear expansion coefficient of the shaft material (stainless steel) is usually 16 × 10 ^-6 /
Assuming that K, the coefficient of linear expansion in the radial direction near the shaft press-fitting portion of the resin molded product needs to be 12 × 10 ⁻⁶ / K to 20 × 10 ⁻⁶ / K. Generally, the coefficient of linear expansion of the resin is large, and in the case of thermoplastic resin, polyphenylene sulfide is 69 × 10
⁻⁶ / K (Polyplastics 0220A9 catalog value), polyethersulfone 57 × 10 ⁻⁶ / K (Sumitomo Chemical 4100G catalog value), etc. (both at right angles to the resin flow (hereinafter, right angle direction) Only))). In order to lower these linear expansion coefficients and obtain a linear expansion coefficient comparable to that of the shaft material, it is necessary to fill the resin with a material having a lower linear expansion coefficient than the resin material. For example, carbon fiber has a linear expansion coefficient of -1 × 10 ⁻⁶ / K to 5 × 10 ⁻⁶ / K, and a resin composite material filled with carbon fiber has a low linear expansion coefficient (for example, polyplastics). S 2
43 × 10 ^{-6 for} 130A1 (carbon fiber filled grade)
/ K (right angle direction), 0 × 10 ⁻⁶ / K (resin flow direction (hereinafter referred to as flow direction)), Sumitomo Bakelite MK20
1 (carbon fiber-filled grade) is 25 × 10 ⁻⁶ / K (perpendicular direction) and 5 × 10 ⁻⁶ / K (flow direction)). The filler is not necessarily carbon fiber.If the coefficient of linear expansion is smaller than that of the resin material, the filler is filled with a fiber, a filler, a granular material, a plate-like material or an amorphous material made of an organic, inorganic or metal material. You may.

Incidentally, the resin composite material often has a different linear expansion coefficient between the flow direction and the direction perpendicular to the flow direction due to the anisotropy of the filler. The linear expansion coefficient is larger in the perpendicular direction than in the flow direction. However, the resin flow is also complicated due to the complicated shape of the mold in a normal resin molded product, and various numerical values are shown depending on each part of the molded product. That is, the coefficient of linear expansion is distributed between the value in the flow direction and the value in the perpendicular direction. In the present embodiment, it is desirable to use a resin composite material having a small difference in linear expansion coefficient between the flow direction and the perpendicular direction. Actually, there is a resin composite material in which the anisotropy of the linear expansion coefficient is small and the value falls within the above-mentioned range of the linear expansion coefficient (the linear expansion coefficient of Sumitomo Bakelite MK205 is 16 × 10 ⁻⁶ / K (perpendicular direction). ), 15 × 10 ⁻⁶ / K (flow direction)).

However, even if the linear expansion coefficient of the resin composite material is anisotropic, it is possible to control the linear expansion coefficient to some extent by providing the gate position in consideration of the resin flow direction including the mold shape. . FIG. 4 is a diagram for explaining the gate position. As shown in FIG. 4, if a film gate over the entire circumference is arranged on a molding die corresponding to a portion 9 a near the shaft press-fitting portion of the fixed drum 9, the resin flows in the longitudinal direction of the shaft 10. As a result, the coefficient of linear expansion in the radial direction near the shaft press-fitting portion is close to the value of the coefficient of linear expansion in the perpendicular direction. On the other hand, if the gate is arranged at one point of the molding die corresponding to 9b, the ratio of the resin flowing in the circumferential direction increases, and the coefficient of linear expansion in the radial direction near the shaft press-fitting portion is:
It approaches the linear expansion coefficient in the flow direction.

FIG. 9 shows an example of these molds. FIG.
(A) is a cross-sectional view when a gate is provided at a portion corresponding to 9a in FIG. As shown in the figure, the molds 50a, b,
The cavity 51 is defined by c, d, e, and f. The resin composite material is introduced from the sprue 52 and flows into the cavity 51 from the gate 9a. When such a mold is used, the resin composite material flows in the axial direction at the shaft press-fitting portion 9c. FIG. 9B is a cross-sectional view when a gate is provided at a portion corresponding to 9b in FIG.
As shown in this figure, the dies 60a, b, c, d, e, f
Defines the cavity 61. The resin composite material is introduced from the sprue 62 and flows into the cavity 61 from the gate 9b via the runner 63. When such a mold is used, the resin composite material flows in the radial direction in the shaft press-fitting portion 9c.

As described above, by adjusting the gate position of the mold in accordance with the linear expansion coefficients of the resin composite material used in the perpendicular direction and the flow direction, the linear expansion coefficient in the vicinity of the shaft press-fit portion can be reduced to some extent. It becomes possible to control. However, the coefficient of linear expansion in the vicinity of the shaft press-fitting portion due to a change in the use temperature must be within the above-mentioned range of the linear expansion coefficient as a part of the resin molded product, not only in the vicinity of the shaft press-fitting portion.

On the other hand, when the flow direction of the resin in the mold cannot be largely changed due to a weld problem or the like,
The radial direction near the shaft press-fitting portion may not coincide with the flow direction of the resin composite material or the direction perpendicular thereto. In this case, in order to make the coefficient of linear expansion in the radial direction near the shaft press-fit portion substantially equal to the coefficient of linear expansion of the shaft, the absolute value and the anisotropy of the coefficient of linear expansion of the resin composite material to be used are limited. There is a need.

If the resin composite material has anisotropy, distortion may occur in the circumferential direction due to the difference in the coefficient of linear expansion between the circumferential direction of the bottom surface and the radial direction. However, since the fixed drum has the notch shape, the elastic modulus near the notch shape in the circumferential direction becomes small, and there is an effect of absorbing distortion. For this reason, distortion at the tape sliding position in the circumferential direction is reduced. In addition, naturally, even if this problem is solved, no distortion occurs when a resin composite material having no linear expansion coefficient is used.

Next, a method of selecting a material to be used when the linear expansion coefficient of the resin composite material is anisotropic will be described. FIG. 5 is a sectional view of the fixed drum for explaining this selection method.

As shown in FIG. 5, the resin molded article is divided into two blocks, ie, a shaft press-fitting portion 11 and a bottom portion 12.
Here, it is assumed that the following assumption is made. 2
Although the ratio of the amount of distortion of one block differs depending on the Poisson's ratio of the resin composite material, it is approximately 11 near the axial press-fit portion: 12: bottom portion 12 = 2: 1. Assuming that the amount of strain generated at the interface between the two blocks is δ, the amount of strain transmitted to the inner diameter portion where the axial press-fitting is performed is substantially the same, and the bottom portion 12 has a radius as a result of resin flowing in the radial direction. 10 × linear expansion coefficient
It becomes lower than the linear expansion coefficient in the radial direction in the vicinity of the shaft press-fit portion by 10 ⁻⁶ / K.

At this time, the vicinity 11 of the shaft press-fitting portion and the bottom portion 12
When the temperature rise is 60 ° C.,
It becomes 4.8 μm. This distortion is caused by the shaft 13 and the vicinity 1 of the shaft press-fitting portion.
From the above, the amount of distortion when transmitted to the interface with No. 1 is calculated to be about 3.2 μm in the direction to increase the shaft fastening force. On the other hand, if the difference in the amount of thermal expansion between the shaft 13 and the vicinity of the shaft press-fitting portion 11 due to the temperature rise of 60 ° C. is 3.2 μm in the direction in which the shaft fastening force is loosened, the amount of distortion and the amount of slack are mutually reduced. Is countered. For this purpose, the linear expansion coefficient in the radial direction of the vicinity 11 of the shaft press-fitting portion is only the linear expansion coefficient of the shaft 13 of 16 × 10
29 × 10 ^-6 / K which is 13 × 10 ^-6 / K larger than ^-6 / K
It is desirable that Specifically, considering that the allowable strain amount is 1 μm, the linear expansion coefficient in the radial direction of the vicinity 11 of the shaft press-fitting portion 11 alone is from 25 × 10 ⁻⁶ / K to 34 × 10 ⁻⁶ / K.
Must be within the range.

Therefore, as the resin composite material to be used, a fixed drum as shown in FIG. 5 was actually prepared, and the linear expansion coefficient of the vicinity 11 of the shaft press-fitting portion (only the linear expansion coefficient near the shaft press-fitting portion 11 of FIG. (Measured by measuring them by dividing them between the parts 12) from 25 × 10 ⁻⁶ / K to 34 × 1
0 ^-6 / K may be a range selected so as something within.

[0039]

According to the present invention, by adjusting the coefficient of linear expansion in the vicinity of the shaft press-fitting portion of the resin molded product to the same level as the shaft to be press-fitted, the resin molded product generated by the change in the operating temperature after the shaft press-fitting is obtained. It reduces the amount of distortion and the reduction in the shaft fastening force.
For this reason, it is possible to obtain a fixed drum having the required high dimensional accuracy.

Further, the fixed drum constituting the rotary head drum device is formed of a resin composite material, and a distortion stress such as a tapered portion, a slit-shaped portion and a step-shaped portion is dispersed between the shaft press-fitting portion and the tape sliding portion. By providing the absorbing strain suppressing portion, the amount of strain propagation to the tape sliding portion at the time of axial press-fitting can be reduced, and the dimensional accuracy of the tape sliding portion can be increased.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a fixed drum having a tapered portion.

FIG. 2 is a cross-sectional view illustrating an example of a fixed drum having a slit-shaped portion.

FIG. 3 is a cross-sectional view showing an example of a fixed drum having a stepped portion.

FIG. 4 is an enlarged view of the vicinity of a shaft press-fitting portion of a fixed drum for explaining a gate position in consideration of a resin flowing direction.

FIG. 5 is a simple model for explaining a method of selecting a resin composite material having anisotropy.

FIG. 6 is a perspective view showing an example of a configuration of a rotary head drum device.

FIG. 7 is a cross-sectional view illustrating an example of the shape of a fixed drum.

FIG. 8 is a perspective view illustrating a cutout portion of the fixed drum.

FIG. 9 is a cross-sectional view illustrating an example of a mold.

[Explanation of symbols]

 1 Rotary drum 2, 6, 7, 8 Fixed drum 2a Cutout part 5 Shaft 6c, 7c, 8c Shaft press-fitting part 6b, 7b, 8b Tape sliding contact part 6a Tapered part 7a Slit shape part 8a Stepped part 11 Shaft press-fit Near the part

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuya Kitamura 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka F-term (reference) 5D036 AA16 BB02 CC04 CC23

Claims (3)

[Claims] 1. A resin having a rotating drum for supporting a magnetic head, a shaft for rotatably supporting the rotating drum, a shaft press-fitting portion for fixing the shaft, and a tape sliding portion for guiding the running of the magnetic tape. A fixed drum made of a composite material, wherein the fixed drum is formed such that a coefficient of linear expansion in a radial direction near the shaft press-fitting portion is substantially equal to a coefficient of linear expansion of the shaft. A rotary head drum device characterized in that: 2. The rotary head drum device according to claim 1,
The radial expansion coefficient in the radial direction near the shaft press-fitting portion is 12 × 10
^-6/ K to 20 × 10 ^-6/ K
Characterized rotary head drum device. 3. The rotating head drum device according to claim 2, wherein a distortion between the shaft press-fitting portion and the tape sliding contact portion of the fixed drum, which suppresses a strain caused by the press-fitting of the shaft, is provided. A rotary head drum device, wherein the suppressing portion is provided coaxially.